UPS for new build

So this never occured to me, I am building my computer and realized that I didn't have any power protection. What should I be looking for in a UPS? I'm using the corsair 650 w power supply. I'd like to get something good, but not something that costs 699 bucks.

UPS (Uninterruptible Power Supply):http://www.newegg.com/Product/Produc...82E16842101494
To provide a short time of uninterrupted power in case of a blackout, so you can backup/save data you would otherwise lose. Also incorporates the above surge protection.
This device can provide up to 390W, which could be tight, depending on your hardware. If you take my computer (see signature) as a reference, this UPS would be enough for me, even in a worst-case scenario:
- 100W CPU
- 150W GPU
- 50W HDDs/DVD
- 40W MB+RAM
- 60W TFT+Speakers+Mouse+Keyboard
= 400W
But this are numbers under maximum stress (like Prime95 with OC + Furmark + HDD Bench). A more realistic approach while gaming would be:
- 50W CPU
- 100W GPU
- 20W HDDs/DVD
- 40W MB+RAM
- 60W Peripherals
= 270W